In some systems, a scanning region of a print surface is scanned with a scanning beam cyclically deflected with a rotating light deflector. The scanned region of the print surface is later transferred to the printed page. The scanning beam is detected by a light sensor which generates a synchronizing “beam detect” signal. Some laser printers use the “beam detect” signal to signal the start of each successive line of data being sent from the scanning laser beam to the printed page. Techniques exist for synchronizing printing to the beam detect signal within a single pixel clock cycle. A drawback of these techniques is that a misalignment of up to one pixel may result.
Another technique involves the passing of a main clock signal through a serially chained series of gates. Each gate delays the clock by a small amount. The resultant skewed clocks are sent as output from the system after each gate delay. The skewed clock most closely aligned with the “beam detect” signal is selected. The skewed clock approach does not work well because of the extensive gating logic required to generate the clocks. For example, because of the extent of logical gating needed, the clock cannot run quickly enough for satisfactory alignment resolution of a printer.
Thus, there is a need for apparatus, methods, and systems for image alignment that use less gating logic and allow the clock to effectively run at higher frequencies.